TY - JOUR
T1 - Gravitational anomalies in string-inspired cosmologies
T2 - 2019 Corfu Summer Institute "School and Workshops on Elementary Particle Physics and Gravity", CORFU 2019
AU - Mavromatos, Nikolaos E.
N1 - Funding Information:
†Work supported in part by the STFC (UK) Research Council through the grants ST/P000258/1 and ST/T000759/1, and by the COST Association Action CA18108 “Quantum Gravity Phenomenology in the Multimessenger Approach (QG-MM)”. NEM also acknowledges a scientific associateship (“Doctor Vinculado”) at IFIC-CSIC-Valencia University, Valencia, Spain.
Publisher Copyright:
© 2019 Sissa Medialab Srl. All rights reserved.
PY - 2019
Y1 - 2019
N2 - In this talk, I review briefly a scenario for the evolution of a string-inspired cosmological model, in which condensates of primordial gravitational waves (GW), formed at the very early eras after the Big Bang, are considered responsible for inducing inflation and then a smooth exit to a radiation dominated epoch. Primordial axion fields, that exist in the fundamental massless gravitational (bosonic) string multiplet, couple to the non-trivial GW-induced anomalies. As a result of this coupling, there exist axion background configurations which violate (spontaneously) Lorentz symmetry, and remain undiluted at the end of inflation. In models with heavy sterile right-handed neutrinos (RHN), such backgrounds are linked to novel (Lorentz and CPT Violating) mechanisms for the generation of matter-antimatter asymmetry in the Cosmos, via the asymmetric decays of the RHN to standard model particles and antiparticles. During the QCD epoch, the axions develop an instanton-induced mass and can, thus, play the rôle of Dark Matter (DM). The energy density of such a Universe, throughout its evolution, has the form of that of a "running vacuum model", that is, it can be expanded in power series of even powers of the Hubble parameter H(t). The coefficients of those terms, though, are different for the various cosmological epochs. For the phenomenology of our model, which is consistent with the current cosmological data, and could also help in alleviating (some of) the tensions, it suffices to consider up to and including quartic powers of H(t). In the early Universe phase, it is the H4(t) term, induced by the GW condensate of the gravitational anomaly, that drives inflation without the need for external inflaton fields.
AB - In this talk, I review briefly a scenario for the evolution of a string-inspired cosmological model, in which condensates of primordial gravitational waves (GW), formed at the very early eras after the Big Bang, are considered responsible for inducing inflation and then a smooth exit to a radiation dominated epoch. Primordial axion fields, that exist in the fundamental massless gravitational (bosonic) string multiplet, couple to the non-trivial GW-induced anomalies. As a result of this coupling, there exist axion background configurations which violate (spontaneously) Lorentz symmetry, and remain undiluted at the end of inflation. In models with heavy sterile right-handed neutrinos (RHN), such backgrounds are linked to novel (Lorentz and CPT Violating) mechanisms for the generation of matter-antimatter asymmetry in the Cosmos, via the asymmetric decays of the RHN to standard model particles and antiparticles. During the QCD epoch, the axions develop an instanton-induced mass and can, thus, play the rôle of Dark Matter (DM). The energy density of such a Universe, throughout its evolution, has the form of that of a "running vacuum model", that is, it can be expanded in power series of even powers of the Hubble parameter H(t). The coefficients of those terms, though, are different for the various cosmological epochs. For the phenomenology of our model, which is consistent with the current cosmological data, and could also help in alleviating (some of) the tensions, it suffices to consider up to and including quartic powers of H(t). In the early Universe phase, it is the H4(t) term, induced by the GW condensate of the gravitational anomaly, that drives inflation without the need for external inflaton fields.
UR - http://www.scopus.com/inward/record.url?scp=85091635090&partnerID=8YFLogxK
M3 - Conference paper
AN - SCOPUS:85091635090
SN - 1824-8039
VL - 376
JO - Proceedings of Science
JF - Proceedings of Science
M1 - 008
Y2 - 31 August 2019 through 25 September 2019
ER -